Connecting techniques for stacked cmos devices

ABSTRACT

In some embodiments, the present disclosure relates to an integrated chip. The integrated chip includes a semiconductor substrate, and an inter-tier interconnecting structure disposed within the semiconductor substrate. The inter-tier interconnect structure includes a first connection point at a lower surface of the inter-tier interconnecting structure and a second connection point at an upper surface of the inter-tier interconnecting structure. The first connection point and the second connection point are not vertically aligned. The inter-tier interconnecting structure includes one or more conductive layers extending between the first and second connection points.

REFERENCE TO RELATED APPLICATION

This Application is a Divisional of U.S. application Ser. No. 15/219,357filed on Jul. 26, 2016, which is a Continuation of U.S. application Ser.No. 14/102,548 filed on Dec. 11, 2013 (now U.S. Pat. No. 9,443,758issued on Sep. 13, 2016). The contents of the above-referenced mattersare hereby incorporated by reference in their entirety.

BACKGROUND

A stacked CMOS chip is a kind of integrated circuit having multipledevice tiers which are vertically stacked and which share one package.Stacked CMOS chips extend chip structure to three dimensions andincrease the number of CMOS devices that can be “squeezed” into a givenfootprint.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective-sectional view of a stacked CMOS devicein accordance with some embodiments.

FIG. 2 illustrates a perspective-sectional view of a stacked CMOS devicein accordance with some alternative embodiments.

FIG. 3 and FIG. 4 illustrate perspective-sectional views of a three-stepstructure of a horizontal connecting structure and a four-step structureof a horizontal connecting structure.

FIG. 5 illustrates a flow diagram of some embodiments of methods forconnecting stacked CMOS devices.

FIGS. 6A-6E illustrate perspective-sectional views of some embodimentsof methods for connecting stacked CMOS devices.

DETAILED DESCRIPTION

The description herein is made with reference to the drawings, whereinlike reference numerals are generally utilized to refer to like elementsthroughout, and wherein the various structures are not necessarily drawnto scale. In the following description, for purposes of explanation,numerous specific details are set forth in order to facilitateunderstanding. It will be appreciated that the details of the figuresare not intended to limit the disclosure, but rather are non-limitingembodiments. For example, it may be evident, however, to one of ordinaryskill in the art, that one or more aspects described herein may bepracticed with a lesser degree of these specific details. In otherinstances, known structures and devices are shown in block diagram formto facilitate understanding.

Relative to packaging solutions where multiple chips are arranged inseparate horizontally spaced packages, stacked CMOS devices (whichinclude multiple chips that are vertically “stacked” over one another ina single package), shrink the lateral footprint for the circuits whenarranged within a product. However, the vertical dimension of stackedCMOS devices can become an issue in some applications. For example,stacked CMOS chips can be too thick for some ultra-thin apparatuses,such as cell phones or portable entertainment units. In addition,forming electrical connections between different vertical device tiersrequires alignment of corresponding contact points on the correspondingdevice tiers, which limits flexibility in structure design. Therefore,in a stacked semiconductor integrated circuit in accordance with someembodiments, instead of connecting multiple tiers solely by a verticalinterwafer via, a multi-layer horizontal connecting structure isfabricated inside a substrate of an individual device tier. Individuallayers of the multi-layer horizontal connecting structure have differentpatterns as viewed from above the substrate. Relative to conventionalapproaches, stacked CMOS devices with multi-layer horizontal connectingstructures provide several advantages. For example, locations ofelectrical contact points of different tiers are flexible, metal usagefor electrical path layers is reduced, and the number of and/orthickness of electrical path layers is decreased which tends to “thindown” chip thickness. Power dissipation is also reduced.

FIG. 1 illustrates a perspective-sectional view of a stacked CMOS device100 in accordance with some embodiments. The stacked CMOS device 100includes multiple device tiers, such as a first device tier 102 and asecond device tier 116. The first device tier 102 comprises a firstsubstrate 104 and a first plurality of devices 106. The second devicetier 116 comprises a second substrate 118 and a second plurality ofdevices 120. A first inter-tier horizontal interconnecting structure 108is formed at least partially inside the first substrate 104. The firstinter-tier horizontal structure 108 electrically connects one or moredevices, such as device 106, on the first substrate 104, to one or moredevices, such as device 120, on the second substrate 118. The firstinter-tier horizontal interconnecting structure 108 can comprisesmultiple conductive layers, such as metal layers, with differentpatterns as viewed from above the first substrate.

The first inter-tier horizontal structure 108 includes a firstconductive layer 110, which takes the form of a vertical connectionelement in this example. The first conductive layer 110 is coupled to asecond conductive layer 112, which takes the form of a first horizontallayer in this example. The second conductive layer 112, which takes theform of a first horizontal layer in this example, is disposed above thefirst vertical connection element 110 and is connected to a device ofthe first plurality of devices 106 or other contact paths on the firstdevice tier 102, for example, power, ground or signal pins. The secondconductive layer 112 is electrically coupled to the device of the seconddevice tier 116 by the first vertical connection element 110. The firstconductive layer 110 couples the second conductive layer 112 (and hencedevice 106) to an electrical interconnect structure 115 on the seconddevice tier 116. The electrical interconnect structure 115 has multiplemetal layers, such as 113 and 114. These metal layers 113 and 114 arearranged under a back side of the first substrate 104 and are coupled toa device 120 of the second device tier 116. The electrical interconnectstructure 115 can also be coupled to other contact points of the seconddevice tier 116 stacked under the first device tier 102. The electricalinterconnect structure 115 can either be formed in a dielectric layerbetween the first tier 102 and the second tier 116 or can be coupledinto the second tier 116.

The first plurality of devices 106 on the first substrate 104 and thesecond plurality of devices 120 on the second substrate 118 can be twodimensional structures (e.g., planar MOSFETs) or three dimensionsstructures (e.g., silicon on insulator (SOI) devices or FinFET devices).The first inter-tier horizontal interconnecting structure 108 in thefirst substrate 104 can be copper, silver, tungsten or aluminum with atantalum (Ta), titanium (Ti), tantalum nitride (TaN), titanium tungsten(TiW), titanium tungsten nitride (TiWN), or titanium nitride (TiN)barrier for preventing metal diffusions. A dielectric layer is formedsurrounding the barrier layer for electrical isolation. The firstsubstrate 104 can be either bulk Silicon or epitaxial Silicon on adielectric material. To further reduce metal material, reduce layers, ordecrease complexity of the electrical interconnect structure 115, thefirst device tier 102 can have devices on both sides. The first devicetier 102 can also be “flipped” over relative to what is shown in FIG. 1so that a top side of the first substrate 104 with the first pluralityof devices 106 is proximate to a top side of the second substrate 118with the second plurality of devices 120. In such way, electricalconnections between the first plurality of devices 106 and the secondplurality of devices 120 become more flexible. The first device tier 102can be formed onto the second device tier 116 by deposition, spraycoated, curtain coated, or spin coated. The first device tier 102 canalso be bonded to the second device tier 116.

Thus, FIG. 1 shows an example of a stacked CMOS device 100 with twodevice tiers (e.g., 102, 116) connected by a multi-layer inter-tierhorizontal interconnecting structure 108 in accordance with someembodiments. Some advantages of this structure include improvedplacement and routing flexibility and reduced metal usage and furtherreduction of area and power consumption of the circuit.

FIG. 2 illustrates a perspective-sectional view of a stacked CMOS device200 in accordance with some alternative embodiments. The stacked CMOSdevice 200 shows example embodiments of disclosure that a third devicetier 226 with a third substrate 228 and a third plurality of devices(e.g., 232) can be stacked onto a first device tier 202 and a seconddevice tier 216 similar to 102 and 116 in FIG. 1. More tiers can bestacked onto the third device tier 226. A second horizontal connectingstructure 230 inside the third substrate 218 comprises three layers 220,222 and 224 and electrically connects the first device tier 202 and thethird device tier 226 of which a detailed example perspective-sectionalview is shown in FIG. 3. Notably, the first substrate 204 with the firsthorizontal connecting structure and the third substrate 228 with thesecond horizontal connecting structure can have similar or differentstructure. Horizontal connecting structures can have same or differentnumbers of conductive layers. Patterns of conductive layers can also bedifferent. Thus, FIG. 2 shows another example semiconductor integratedcircuit with more than two device tiers connected by multi-layerinter-tier horizontal interconnecting structures in accordance with somealternative embodiments.

FIG. 3 illustrates a perspective-sectional view of an examplethree-layer structure of a horizontal connecting structure. Thehorizontal connecting structure can be used as either the firsthorizontal connecting structure 208 or the second horizontal connectingstructure 230 in FIG. 2. In the example, a first conductive layer 320 isa first vertical connection element electrically coupled to a device ofa device tier thereunder. A second conductive layer 322 is a firsthorizontal layer disposed above the first vertical connection element320 and a third conductive layer 324 is a second horizontal layerdisposed above the first horizontal layer 322 and electrically coupledto a device on a substrate 304 of a device tier 326 thereon through boththe first conductive layer 320 and the second conductive layer 322. Alocation of at least a portion of the first conductive layer 320 shiftshorizontally to a location of the second conductive layer 322 or thethird conductive layer 324. The first conductive layer 320 connectscontact points such as 326 and 328 on the other side of a substrate 304not vertically aligned with a location of the first conductive layer 320through the second conductive layer 322 and the third conductive layer324. The first conductive layer 320, which is a vertical connectionelement in the illustrated example, can have a square-like or roundedperimeter as viewed from above and can fall within edges of secondconductive layer. In some embodiments, 320 is formed along Z direction,322 is formed along Y direction, 324 is formed along X direction. Insome embodiments, 320, 322, 324 are in perpendicular with each other inrespective X, Y, Z direction. In some embodiments, 304 includes anynumber of conductive layers. In some embodiments, any two conductivelayers of the conductive layers in 304 are in parallel or inperpendicular with each other.

FIG. 4 illustrates a perspective-sectional view of a four-layerhorizontal connecting structure 400 comprising an additional fourthconductive layer. The four layer horizontal connecting structure 400 canbe used as either the first horizontal connecting structure 208 or thesecond horizontal connecting structure 230 in FIG. 2. In FIG. 4'sexample, a first conductive layer 420 is a first vertical connectionelement extending in the z-direction and which is electrically coupledto a device of a device tier (not shown) thereunder. A second conductivelayer 422 is a first horizontal layer disposed above the first verticalconnection element 420 and extending in the y-direction. A thirdconductive layer 423 is a second vertical connection element connectingthe second conductive layer 422 to a fourth conductive layer 424. Thefourth conductive layer 424 is a second horizontal layer which extendsin the x direction and which is disposed above the second verticalconnection element 423. The first conductive layer 420 is electricallycoupled to a device on a substrate 404 of device tier 426 through thesecond conductive layer 422, the third conductive layer 423, and thefourth conductive layer 424. Structures of FIG. 3 and FIG. 4 can beapplied to any upper level tier (e.g. the tier 102 of 100 and tier 202or 226 of 200) of disclosed stacked CMOS devices.

FIG. 5 illustrates a flow diagram of some embodiments of methods forconnecting stacked CMOS tiers in accordance with some embodiments. Whiledisclosed methods (e.g., methods 500 of FIG. 5) are illustrated anddescribed below as a series of acts or events, it will be appreciatedthat the illustrated ordering of such acts or events are not to beinterpreted in a limiting sense. For example, some acts may occur indifferent orders and/or concurrently with other acts or events apartfrom those illustrated and/or described herein. In addition, not allillustrated acts may be required to implement one or more aspects orembodiments of the description herein. Further, one or more of the actsdepicted herein may be carried out in one or more separate acts and/orphases.

At 502, a first device tier with a first substrate including a firstplurality of devices is formed.

At 504, a second substrate is applied on the first device tier.

At 506, a first conductive layer is formed in the second substrateelectrically connecting to a device on the first substrate.

At 508, a second conductive layer is formed in the second substrate.

At 510, a second plurality of devices and electrical connections areformed on the second substrate.

One example of FIG. 5's method is now described with regards to a seriesof cross-sectional views as shown in FIGS. 6a-6e . Although 6 a-6 e aredescribed in relation to method 500, it will be appreciated that thestructures disclosed in FIGS. 6a-6e are not limited to such a method,but instead may stand alone as a structure.

At FIG. 6a , a first device tier 602 with a first substrate 618 and afirst plurality of devices is formed. An electrical path 615 withmultiple layers of metal is formed onto the first substrate inside adielectric layer 630. The multiple layers of metal can be copper,silver, tungsten or aluminum, for example.

At FIG. 6b , a second substrate 604 is applied on the first device tier602. The second substrate can be formed by deposition, such as epitaxialdeposition for example, or can be bonded to the second device tier 116.For example, in some embodiments, the first device tier can correspondto a first bulk silicon wafer, and the second device tier can correspondto a second bulk silicon wafer, wherein the first wafer has a backside(or topside) that is bonded to the topside of the second bulk siliconwafer.

At FIG. 6c , after the second substrate has been applied to the firstsubstrate, a first conductive layer 610 is formed in the secondsubstrate. The first conductive layer 610 electrically connecting to adevice on the first substrate 618. For example, the first conductivelayer 610 can be copper, silver, tungsten or aluminum with a tantalum(Ta), titanium (Ti), tantalum nitride (TaN), titanium tungsten (TiW),titanium tungsten nitride (TiWN), or titanium nitride (TiN) barrier (notshown) for preventing metal diffusions. A dielectric layer (not shown)is formed surrounding the barrier layer for electrical isolations.

At FIG. 6d , a second conductive layer 612 is formed in the secondsubstrate 604. For example, the second conductive layer 612 can becopper, silver, tungsten or aluminum with a tantalum (Ta), titanium(Ti), tantalum nitride (TaN), titanium tungsten (TiW), titanium tungstennitride (TiWN), or titanium nitride (TiN) barrier for preventing metaldiffusion, and also form dielectric layer surrounding the barrier layerfor electrical isolation.

At FIG. 6e , a second plurality of devices and electrical connectionsare formed on the second substrate. One or more of the second pluralityof devices on the second substrate are electrically coupled to one ormore of the first plurality of devices on the first substrate.

Thus, the present disclosure relates to an integrated chip having aninter-tier interconnecting structure with horizontal components, whichis arranged within a semiconductor substrate and that is configured toelectrically couple a first device tier to a second device tier.

In some embodiments, the disclosure relates to an integrated circuit.The integrated chip comprises a first device tier having a firstsemiconductor substrate. A first inter-tier interconnecting structure isdisposed inside the first semiconductor substrate and comprises a firstsegment extending in a first direction and a second segment protrudingoutward from a sidewall of the first segment in a second directionsubstantially perpendicular to the first direction. A second device tieris electrically coupled to the first device tier by the first inter-tierinterconnecting structure.

In other embodiments, the disclosure relates to an integrated circuit.The integrated chip comprises a first device tier having a firstsemiconductor substrate. An inter-tier interconnecting structure isdisposed within the first semiconductor substrate. The inter-tierinterconnect structure comprises a first connection point at a lowersurface of the inter-tier interconnecting structure and a secondconnection point at an upper surface of the inter-tier interconnectingstructure. The first connection point and the second connection pointare not vertically aligned. The inter-tier interconnecting structurecomprises one or more conductive layers extending between the first andsecond connection points.

In yet other embodiments, the disclosure relates to an integratedcircuit. The integrated chip comprises a first device tier having afirst inter-tier interconnecting structure arranged inside a firstsemiconductor substrate. The first inter-tier interconnecting structurecomprises a first conductive layer and a second conductive layer withdifferent patterns. A second device tier is electrically connected tothe first device tier by the first inter-tier interconnecting structure.

It will be appreciated that while reference is made throughout thisdocument to exemplary structures in discussing aspects of methodologiesdescribed herein (e.g., the structure presented in FIGS. 6a-6e , whilediscussing the methodology set forth in FIG. 5), that thosemethodologies are not to be limited by the corresponding structurespresented. Rather, the methodologies (and structures) are to beconsidered independent of one another and able to stand alone and bepracticed without regard to any of the particular aspects depicted inthe Figs. Additionally, layers described herein, can be formed in anysuitable manner, such as with spin on, sputtering, growth and/ordeposition techniques, etc.

Also, equivalent alterations and/or modifications may occur to thoseskilled in the art based upon a reading and/or understanding of thespecification and annexed drawings. The disclosure herein includes allsuch modifications and alterations and is generally not intended to belimited thereby. For example, although the figures provided herein, areillustrated and described to have a particular doping type, it will beappreciated that alternative doping types may be utilized as will beappreciated by one of ordinary skill in the art.

In addition, while a particular feature or aspect may have beendisclosed with respect to only one of several implementations, suchfeature or aspect may be combined with one or more other features and/oraspects of other implementations as may be desired. Furthermore, to theextent that the terms “includes”, “having”, “has”, “with”, and/orvariants thereof are used herein, such terms are intended to beinclusive in meaning—like “comprising.” Also, “exemplary” is merelymeant to mean an example, rather than the best. It is also to beappreciated that features, layers and/or elements depicted herein areillustrated with particular dimensions and/or orientations relative toone another for purposes of simplicity and ease of understanding, andthat the actual dimensions and/or orientations may differ substantiallyfrom that illustrated herein.

What is claimed is:
 1. An integrated circuit, comprising: asemiconductor substrate; an inter-tier interconnecting structuredisposed within the semiconductor substrate and comprising a firstconnection point at a lower surface of the inter-tier interconnectingstructure and a second connection point at an upper surface of theinter-tier interconnecting structure, wherein the first connection pointand the second connection point are not vertically aligned; and whereinthe inter-tier interconnecting structure comprises one or moreconductive layers extending between the first and second connectionpoints.
 2. The integrated circuit of claim 1, wherein the inter-tierinterconnecting structure comprises a first segment extending in a firstdirection and a second segment protruding outward from a sidewall of thefirst segment in a second direction substantially perpendicular to thefirst direction.
 3. The integrated circuit of claim 1, wherein theinter-tier interconnecting structure comprises a first conductive layerand a second conductive layer having a different footprint than thefirst conductive layer.
 4. The integrated circuit of claim 3, whereinthe second conductive layer laterally extends past a sidewall of thefirst conductive layer.
 5. The integrated circuit of claim 3, furthercomprising: a semiconductor device arranged along a first side of thesemiconductor substrate; wherein sidewalls of the semiconductorsubstrate define a trench extending within the first side of thesemiconductor substrate and comprising a rectangular shape; and whereinthe second conductive layer is disposed within the trench.
 6. Theintegrated circuit of claim 3, wherein the second conductive layercomprises a first segment contacting a first point along an uppersurface of the first conductive layer and a non-continuous secondsegment contacting a second point along the upper surface of the firstconductive layer; and wherein the first segment and the second segmentare completely separated by the semiconductor substrate.
 7. Theintegrated circuit of claim 1, wherein the inter-tier interconnectingstructure comprises a “T” shape as viewed along a cross-section of thesemiconductor substrate.
 8. The integrated circuit of claim 1, whereinthe inter-tier interconnecting structure extends from within thesemiconductor substrate to a position that is below a bottommost surfaceof the semiconductor substrate.
 9. An integrated circuit, comprising: asemiconductor substrate; and an inter-tier interconnecting structuredisposed within the semiconductor substrate, wherein the inter-tierinterconnecting structure comprises a first segment extending in a firstdirection and a second segment protruding outward from a sidewall of thefirst segment in a second direction that is substantially perpendicularto the first direction.
 10. The integrated circuit of claim 9, whereinthe inter-tier interconnecting structure comprises: a first conductivelayer disposed inside the semiconductor substrate; and a secondconductive layer disposed inside the semiconductor substrate over thefirst conductive layer and comprising the first segment extending in thefirst direction and the second segment protruding outward from thesidewall of the first segment.
 11. The integrated circuit of claim 10,wherein the first conductive layer and the second conductive layer havedifferent patterns as viewed from above the semiconductor substrate. 12.The integrated circuit of claim 10, further comprising: a thirdconductive layer disposed inside the semiconductor substrate over thesecond conductive layer and having a different pattern than the firstconductive layer and the second conductive layer as viewed from abovethe semiconductor substrate.
 13. The integrated circuit of claim 10,wherein the second conductive layer has a bottommost surface thatextends past the first conductive layer in the first direction and inthe second direction.
 14. The integrated circuit of claim 9, furthercomprising: a semiconductor device arranged along a first side of thesemiconductor substrate, wherein the inter-tier interconnectingstructure comprises a rectangular upper surface extending along thefirst side of the semiconductor substrate.
 15. The integrated circuit ofclaim 9, wherein the inter-tier interconnecting structure comprises an“L” shape as viewed from above the semiconductor substrate.
 16. Anintegrated circuit, comprising: a semiconductor substrate; a firstconductive layer disposed inside the semiconductor substrate and asecond conductive layer disposed inside the semiconductor substrate overthe first conductive layer; and wherein the second conductive layerextends past a sidewall of the first conductive layer.
 17. Theintegrated circuit of claim 16, wherein a first upper connection pointis arranged along an upper surface of the second conductive layer and asecond upper connection point is arranged along the upper surface of thesecond conductive layer at a location separated from the firstconnection point by a non-zero distance.
 18. The integrated circuit ofclaim 16, further comprising: a semiconductor device arranged along afirst surface of the semiconductor substrate, wherein the secondconductive layer extends along a trench within the first surface of thesemiconductor substrate.
 19. The integrated circuit of claim 18, furthercomprising: a dielectric structure disposed on the first surface of thesemiconductor substrate; and a first plurality of conductiveinterconnect layers surrounded by the dielectric structure, wherein thefirst plurality of conductive interconnect layers are coupled to thesecond conductive layer.
 20. The integrated circuit of claim 16, whereinthe first conductive layer and the second conductive layer havedifferent patterns as viewed from above the semiconductor substrate.